Gravity screens are widely used to separate solids from streams of water in order to produce an effluent useful for purposes such as irrigation or acceptability to a sewer, or as a first step in processing solid-laden streams ultimately to produce potable water.
A well-known example of gravity screen systems is shown in Wake U.S. Pat. No. 3,357,567. This patent is incorporated by reference herein its entirety for its showing of systems of this type, and of their utility.
For example, water in irrigation ditches generally is burdened with considerable organic trash and mineral particulates. It is undesirable to dump this material into a crop-growing area. Directing it first through a system according to this invention can clarify the stream to the extent that when applied to crops it is without this burden, and acceptable to crop land.
In addition to agricultural applications, this invention finds utility in many industrial applications where a water stream is used in processes involved in manufacturing or food preparation operations. Washings from vegetables and fruits, and even washings from floors, generate debris-laden streams that require removal of solids before the water can be used again, or before it can be discharged into a sewer.
This invention utilizes a rotating wand below the screen which, as it rotates around a horizontal axis, projects streams of water upwardly against the screen. Rotation of the rotary wand causes the emitted water streams to move along the screen so as to assist movement of the debris along the screen, as well as to prevent the screen perforations from becoming clogged.
The foregoing is known art, but it has suffered from a lack of reliable power for rotating the wand. One problem resides in the very slow rotation desired for the wands--on the order of 2 rpm. When sprinkler motors or electric motors are used, problems soon develop because their power and their output do not match the system requirements.
Because this device relates entirely to water systems, and a source of clean-enough water is available from the filter, a pump can be utilized to project a stream of water through a nozzle to a water wheel that can turn at a rapid rate which is greatly reduced by a gear reduction to drive the wand. This provides a powerful drive without a mechanical linkage to an electric motor. If for some reason the wands are stalled, no harm is done to the water wheel. In that unlikely event, it simply stalls and the pump continues to run without unfavorable consequences. The pump supplies water both for backwashing and for powering the wands, and ordinarily utilizes water which has already passed through the screen.
Accordingly it is an object of this invention to provide a compact system which downstream from a pump is entirely hydraulically actuated, and in which hose connections can be appreciably shortened and in many applications eliminated entirely.